1. Field of the Invention
The invention concerns a support and guidance unit for a sliding door of a motor vehicle. More specifically, the invention relates to sliding side doors on recreational or commercial vehicles.
2. Description of the Related Art
Motor vehicle sliding doors, comprising a support and guidance system constituted by a support roller and two guide rollers are known. The support roller is mounted so as to be freely moving when rotating around a horizontal shaft, while the two guide rollers are freely-moving when rotating around two vertical parallel shafts. When mounted, the unit is located in a rail with a hollow profile of rectangular cross-section, so that it can slide along this rail. To allow the support and guidance unit to move, the distance between the two walls of the hollow profile is slightly greater than the diameter of the guide roller.
Consequently, when the door slides between its open and closed positions, the guide rollers are not always in contact with the wall of the profile and collide alternately with both walls, generating unpleasant noise for the passengers of the motor vehicle as well as the operator of the sliding door. Moreover, the support rollers are usually manufactured by forging. The die separation surface cuts the running surface. Consequently, the forged roller has to be thoroughly deburred to avoid damaging the guide rail running surface. The process of deburring is expensive. In addition, such support and guidance units comprise many parts, which makes them expensive to produce and assemble.
The objective of the invention is to circumscribe these drawbacks and to recommend a support and guidance unit that generates very little noise during operation, and is easy and economical to manufacture, while ensuring efficient side door guidance when sliding. For this purpose, this invention concerns a unit of the aforesaid type, which is a support and guidance unit for a sliding door of a motor vehicle. The support and guidance unit includes a support adapted to be fitted onto a first structure element of a motor vehicle. A roller assembly is rotationally mounted around a first axis Xxe2x80x94X on the support and is adapted to roll on a support and guidance rail. The support and guidance rail is adapted to be fitted onto a second structure element of the motor vehicle and devised to slide with respect to the said first structure element. The roller assembly has two running surfaces extending on both sides of a plane of symmetry Mxe2x80x94M, that extends perpendicularly to the said first axis Xxe2x80x94X in that the normals to the running surfaces have axial components C1, C2 parallel to the first axis and oriented towards opposite directions.